M35 Blowing Smoke >4K Rpm, Hesitation Around 4.5-4.75K

[Dunc]

My car is blowing 'smoke' at around 4k and it gets heavier/thicker as the revs increase. When I hit around 4.5-4.75k there's hesitation almost like hitting a limiter (Not as bad as when you blow an AFM and cant get over 2.5k though). Im still making positive boost, and I don't have a CEL. No weird noises.

Initial thoughts were my AFM throwing bad readings, so I took some readings and it looked slightly suspicious - on idle 1.59v and when Im up around 4.5k RPM it maxes out to 4.64v. Ive since swapped in one of Scottys spares, and it has identical readings on the Informeter. Could it be a bad earth on the AFM circuit that's causing high readings, or are those numbers 'right' - can anyone compare?

Im a bit stumped as to what else to look in to or play with. Suggestions welcome!

Cheers,

Dunc

[PN-Mad]

Those numbers sound in the ball park from those I've tested.

What colour is the smoke, white, black or grey?

[Dunc]

Those numbers sound in the ball park from those I've tested.

What colour is the smoke, white, black or grey?

I'd say black. Could be a bit grey-black I guess? Hard to tell when driving

[PN-Mad]

Yeah, it is hard to tell.

Black is generally fuel smoke, so you need to look for leaks in I/C piping, hoses off the plenum, or any seals in the intake system. Spray joins with brake cleaner and see if the idle note changes. Pull a couple of plugs and inspect to see if excess fuel has been pumping through.

[PN-Mad]

The afm cut is around 5.12v, so your not hitting the flow cut.

[scotty nm35]

Stock afm cut is much lower, around 4.7v the engine start backing out timing etc. Nismo ecu's will be different obviously.

It definitely sounds like a boost leak somewhere...

[PN-Mad]

Stock afm cut is much lower, around 4.7v the engine start backing out timing etc. Nismo ecu's will be different obviously.

It definitely sounds like a boost leak somewhere...

Not from the cars I've logged. And it would be at least 1/2 a dozen running stock ecus.

[lstef11]

im having the same problem i think mate does she smell like your running rich and are you idle rpm a bit higher than normal and a small put every now and then when shes warmed up on idle?

[Mr 20Valve]

Boost leak between the AFM & throttle body.

Either that or its your muffler bearings...

[scotty nm35]

Not from the cars I've logged. And it would be at least 1/2 a dozen running stock ecus.

Argumentative kent. Why don't you help instead NA boy?

Sounds like your logging software is faulty... There is a good reason the EMU needs a clamp at 4.7v for the 25det. Stick to logging the 3.5 with your Osirus crap.

[Dunc]

Stock afm cut is much lower, around 4.7v the engine start backing out timing etc. Nismo ecu's will be different obviously.

It definitely sounds like a boost leak somewhere...

I'm on an impul ecu, so I guess that makes sense that it might have similar afm cut.

Will need to suss out for a boost leak then.

[Dunc]

Boost leak between the AFM & throttle body.

Either that or its your muffler bearings...

:squint:

So any tips as to what specifically between the AFM and TB might leak?

[scotty nm35]

Can you pressure test the intake? Just make up a bung for the rubber pipe and shove 20psi into the front of the turbo, it will quickly tell you if and where any leaks are.

[Jetwreck]

You say you have an impul....from memory they have no restraints. I blew my first motor on an impul.

[PN-Mad]

Argumentative kent. Why don't you help instead NA boy?

Sounds like your logging software is faulty... There is a good reason the EMU needs a clamp at 4.7v for the 25det. Stick to logging the 3.5 with your Osirus crap.

"its easy on my C34"?

I did help... the AFM cut is above 5v. Seen it at 5.08-5.12v. Dont be jelly your China spec Consult can't handle the logging

[Commsman]

I'm with you Alex. My informeter shows above 5V & Uprev has logged above 5 as well. Can't remember exactly what voltage it is when my head bangs into the 'screen, but it's somewhere around 5.15V.

[Dunc]

Yeah, it is hard to tell.

Black is generally fuel smoke, so you need to look for leaks in I/C piping, hoses off the plenum, or any seals in the intake system. Spray joins with brake cleaner and see if the idle note changes. Pull a couple of plugs and inspect to see if excess fuel has been pumping through.

Ive checked all the IC piping and hoses off the plenum, it all feels sufficiently secure but now that Im really listening for it I can hear a bit of a hiss coming from around the centre of the plenum on idle. I went and grabbed some carby cleaner to throw around hoses to see if it changed at all but I couldnt get any difference out of it.

Can you pressure test the intake? Just make up a bung for the rubber pipe and shove 20psi into the front of the turbo, it will quickly tell you if and where any leaks are.

I think that test is outside of my skill set / available tools

I threw a gopro on the back of the car to video the black smoke and 'limiter' hitting, Im not even sure that was hitting 4k on that drive though; so perhaps its getting worse?

[PN-Mad]

Yep, looks like fuel.

You may have fouled the plugs. Pull a couple out, and inspect. That little hiss might be the PCV. You'll have to check all lines for splits as well, maybe the boost gauge or controller lines. Might have blown a intake gasket. Just ideas.

[Jetwreck]

Give me a call if you want.....

[scotty nm35]

I'm with you Alex. My informeter shows above 5V & Uprev has logged above 5 as well. Can't remember exactly what voltage it is when my head bangs into the 'screen, but it's somewhere around 5.15V.

The afm drops out timing and dumps fuel at well below the 'head goes through the windscreen'. Lets just agree to disagree, you two are surely more proficient at this.

Dunc, pressure testing the intake is easy, just grab an old tyre valve and a lid or plumbing cap that fits nicely into the rubber pipe, then use a pump/compressor to fill the intake. (you could even do it at the servo) Just checking if the fittings are loose won't tell you if there is a split in a hose somewhere you can't see.